Why have Prime Timber when it is useless in the first place? I suggest you either remove it or make some building's that require that. For example, after researching Guilds or some other technologies, I be able to build furniture stores that help make my citizens happy. Not only that but if you make it an early important to build structures as well so that Prime Timber will no longer be useless.
Yes and No.
No because I like having this resource on forests. It adds diversity.
Yes because it should increase build time of wooden units by 25%.